title: Melatonin and steroid hormones activate intermembrane Cu,Zn-superoxide dismutase by means of mitochondrial cytochrome P450.
abstract: Melatonin and steroid hormones are cytochrome P450 (CYP or P450; EC 1.14.14.1) substrates that have antioxidant properties and mitochondrial protective activities. The mitochondrial intermembrane space (IMS) Cu,Zn-superoxide dismutase (SOD1) is activated after oxidative modification of its critical thiol moieties by superoxide anion (O₂(•-)). This study was aimed at investigating the potential association between the hormonal protective antioxidant actions in mitochondria and the regulation of IMS SOD1 activity. Melatonin, testosterone, dihydrotestosterone, estradiol, and vitamin D induced a sustained activation over time of SOD1 in intact mitochondria, showing a bell-shaped enzyme activation dose response with a threshold at 50nM and a maximum effect at 1μM concentration. Enzyme activation was not affected by furafylline, but it was inhibited by omeprazole, ketoconazole, and tiron, thereby supporting the occurrence of a mitochondrial P450 activity and O₂(•-) requirements. Mitochondrial P450-dependent activation of IMS SOD1 prevented O₂(•-)-induced loss of aconitase activity in intact mitochondria respiring in State 3. Optimal protection of aconitase activity was observed at 0.1μM P450 substrate concentration, evidencing a likely oxidative effect on the mitochondrial matrix by higher substrate concentrations. Likewise, enzyme activation mediated by mitochondrial P450 activity delayed CaCl₂-induced loss of transmembrane potential and decreased cytochrome c release. Omeprazole and ketoconazole abrogated both protecting mitochondrial functions promoted by melatonin and steroid hormones.
authors.affiliation: Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain. inarrea@unizar.es
authors.forename: Pedro
authors.initials: P
authors.lastname: Iñarrea
authors.forename: Alvaro
authors.initials: A
authors.lastname: Casanova
authors.forename: Maria Angeles
authors.initials: MA
authors.lastname: Alava
authors.forename: María
authors.initials: M
authors.lastname: Iturralde
authors.forename: Enrique
authors.initials: E
authors.lastname: Cadenas
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D016166:Free Radical Scavengers / Q000378:metabolism; D012739:Gonadal Steroid Hormones / Q000494:pharmacology*; D007654:Ketoconazole / Q000494:pharmacology; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D008564:Membrane Potentials; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D009853:Omeprazole / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013482:Superoxide Dismutase / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D012739:Gonadal Steroid Hormones; D003577:Cytochrome P-450 Enzyme System; D013482:Superoxide Dismutase; D008550:Melatonin; D009853:Omeprazole; D007654:Ketoconazole